Modern vehicles typically have one or more diagnostic systems, generally having separate computer control modules to control various functions of the vehicle. Some examples include powertrain control module (PCM), engine control module (ECM), a transmission control module (TCM), Anti-locking brake system (ABS), and an air bag control module. The vehicle diagnostic systems often have self-diagnostic capability to detect and alert the driver of problems the vehicle may be encountering. When a problem is found, a diagnostic trouble code or DTC, is set within the computer's memory. DTCs are as general or as specific as the manufacturer desires.
To retrieve and decipher DTCs, an auto repair technician needs a diagnostic tool. The diagnostic tool must, therefore, be connected to the vehicle's computer bus system to access and retrieve the DTCs. Scan tools are testing devices that interface with vehicle diagnostic systems to retrieve information from the various control modules. The scan tools are equipped to communicate in various communication protocols such as Controller Area Network (CAN), J1850 VPM and PWM, ISO 9141, Keyword 2000 and others. These communications protocols may be specific to the various automobile manufacturers. The scan tool will help the technician to diagnose and repair the vehicle based on the information the tool retrieves from it.
In some instances, manufacturers configure their onboard computers with proprietary protocols where a specialized diagnostic tool is required to communicate with that vehicle. Also, within a manufacturer's fleet of vehicles, certain models may use one communication protocol, while other models may use another communication protocol. Even within a given vehicle, modules may use different communication protocols. This further complicates matters and requires diagnostic tools capable of communicating with various modules and models. One such example is Volvo, who uses different protocols for different models and modules.
Accordingly, it is desirable to provide a method and apparatus that allows a diagnostic tool to successfully communicate with a Volvo vehicle, regardless of the protocol the particular Volvo model uses.